1. Field of the Invention
The present invention relates to a high sensitivity microscope. More particularly, the invention relates to a technology which enables bright observation of a dark specimen image (for example, a specimen unsuitable for the use of strong illumination light), through the use of an image intensifier which may be introduced into a viewing optical system.
2. Related Background Art
Conventional optical microscopes are constructed such that an objective receives light from a specimen irradiated by an illumination device of the microscope and such that imaging optical flux from the objective is guided to an image plane of an eyepiece.
In conventional optical microscopes, strong illumination light must be used in order to obtain a bright microscopic image. However, there are instances in which strong illumination light does not provide a bright image, as well as instances in which strong illumination light is not appropriate for observing a particular specimen. For example, if a specimen has a slight polarization, requiring a polarization microscopic observation, an observed image would be still be dark even with increased illumination light. As another example, for a specimen such as a cultured cell or microorganism which would die under strong illumination light, weak illumination light must be used. This inconveniently results in a dark image which is difficult to observe. The foregoing problems are notably compounded with increased microscope magnification, because an observation image becomes darker as magnification increases. Also, in the case of a fluorescent microscope using a fluorescent specimen, the use of strong illumination light is problematic in that fluorescent color matter in the specimen becomes faded soon after being subjected to the illumination light.
It is possible to utilize a high sensitivity television camera, such an SIT camera, attached to a microscope to enable viewing of an intensified image of a dark specimen on a television monitor. However, observation is limited on the television monitor, so that the field of view is narrow and the resulting system is undesirably large. It is also inconvenient to use such a monitor because the operator must change his view between a lens barrel of the microscope and the monitor when switching observation modes (ordinary microscopic observation versus television observation).